On Aug. 30, 1992, astronomers spotted an object orbiting the sun beyond Pluto for the very first time. It was the first Kuiper Belt object ever detected.
Before then, Pluto was believed to be the most distant planetary body of our solar system. No one had seen anything orbiting farther out because these so-called Trans-Neptunian objects were far too faint to detect with the technology they had at the time.
With new digital imaging techniques, astronomers were able to spot a new and tiny world orbiting 4 billion miles beyond Neptune. Officially designated 1992 QB1, this 100-mile-wide (160 kilometers) object was thousands of times fainter than Pluto. Now astronomers have confirmed more than 2,000 objects orbiting out there in what is now known as the Kuiper Belt.
Why it mattered
Our solar system was a much smaller place before the discovery of 1992 QB-1. We had nine planets, from Mercury to Pluto, and that was the end.
But when astronomers found 1992 QB-1, it led to a much larger solar system than anyone could have dreamed.
The Kuiper Belt, named after the Dutch astronomer Gerard Kuiper who first proposed its existence, is a doughnut-shaped region that begins at the orbit of Neptune, about 2.8 billion miles (4.6 billion miles) from the sun. If you use the distance between the Earth and sun, which is 93 million miles (1 astronomical unit or 1 AU), as a guide, the Kuiper Belt begins about 30 AU from the sun and extends out to 1,000 AU. It’s one of the largest structures in the solar system.
While 1992 QB-1 was the first confirmed Kuiper Belt object after Kuiper theorized the region’s existence, the dwarf planet Pluto — which is also beyond Neptune — was found first in 1930.
Back then, Pluto was classified as a full planet, but the discovery of 1992 QB-1, as well as Kuiper Belt objects even larger than Pluto found later, raised questions about Pluto’s status. An object called Eris, which is larger than Pluto, ultimately led astonomers to downgrade Pluto to a dwarf planet in 2006.
Today, Kuiper Belt objects aren’t just objects in photos, they are places humanity has explored with spacecraft. In 2015, NASA’s New Horizons spacecraft flew by Pluto, a first in history. That probe went on to fly by the Kuiper Belt object Arrokoth on Jan. 1, 2019.
Speaking of finding unseen objects in space, on this day in space (in 2026, it JUST happened), NASA’s Roman Space Telescope launched atop a SpaceX Falcon Heavy rocket to observe more of the universe than ever before. Here’s why that matters.
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